|TOPS design code|Electrical system|Max speed|Weight|Brakes|Route availability|Notes|
|---|---|---|---|---|---|---|
|08-0AV|90 V|20 mph (32 km/h)|49.8 te (496 kN)|vacuum|5||
|08-0BX|110 V|20 mph (32 km/h)|50.4 te (502 kN)|dual|5||
|08-0CA|90 V|20 mph (32 km/h)|49.6 te (494 kN)|air|5||
|08-0DV|90 V|15 mph (24 km/h)|49.8 te (496 kN)|vacuum|5||
|08-0BX|90 V|15 mph (24 km/h)|50.4 te (502 kN)|dual|5||
|08-0FA|90 V|15 mph (24 km/h)|49.6 te (494 kN)|air|5||
|08-0KX|110 V|15 mph (24 km/h)|50.4 te (502 kN)|dual|5||
|08-0LX|110 V|15 mph (24 km/h)|50.4 te (502 kN)|dual|5|Scharfenberg adapter fitted|
|08-0MA|110 V|15 mph (24 km/h)|49.8 te (496 kN)|air|5||
|08-0NA|90 V|15 mph (24 km/h)|49.8 te (496 kN)|air|5|fitted with Buckeye couplings|
|08-0PA|90 V|15 mph (24 km/h)|51 te (508 kN)|air|6|fitted with Buckeye couplings|
|08-0QA|90 V|15 mph (24 km/h)|51 te (508 kN)|air|6|fitted with Buckeye couplings|
|08-0RA|110 V|15 mph (24 km/h)|51 te (508 kN)|air|6|fitted with Buckeye couplings|
|08-0SA|110 V|15 mph (24 km/h)|49 te (488 kN)|air|6||

Question: what's the total design variations with vacuum brakes?
Answer: 2